The number of echoes combined into a single image or image set in multiple echo imaging sequences or echo-train techniques such as rapid acquisition with relaxation enhancement (RARE), fast-spin echo (FSE), and turbo spin-echo (TSE). In RARE imaging, the ETL typically equals the acceleration factor.
As for tooth pain, it is caused by a reaction of the nerves inside a tooth's pulp chamber with the severity dependent upon the type and degree of the stimulus. What follows are some examples of symptoms you may be feeling and their possible causes.
Causes Of Tooth Nerve Pain. Tooth nerve pain is generally caused by inflammation or irritation of the central portion of the tooth, called the dental pulp. The dental pulp contains very sensitive nerve endings that are usually protected by other layers of the tooth, namely the dentin, cementum, and enamel.